Alternatives to diesel fuel have been sought in heavy vehicle applications to reduce dependence on imported oil and to reduce environmental impact of tailpipe emissions. Spark ignited lean burn natural gas fueled engines have found applications in transit buses, school buses and trucks. West Virginia University, through use of one of its Transportable Heavy Duty Vehicle Emissions Testing Laboratories, characterized the emissions of a fleet of school buses in Indio, Ca. The buses were powered by 8.3 liter Cummins natural gas engines employing feedback fueling control, and by conventional 8.3 liter diesel engines. The laboratory employs a chassis dynamometer with flywheels to mimic inertia and air-cooled eddy current power absorbers to account for road load. Exhaust was routed to a full scale dilution tunnel, and regulated gas emissions and particulate matter in the exhaust were measured. The vehicles were exercised through the Central Business District cycle during emissions characterization. Oxides of nitrogen emissions, by mass, were 12% lower for the 11 natural gas buses than for the three diesel control vehicles. Particulate matter was also lower, by 46%, but carbon monoxide for the natural gas busses was six times higher. Although the total hydrocarbons from the natural gas buses were far higher than from the diesel units, the bulk of the natural gas hydrocarbon emissions were methane, which is not an ozone forming species. The non-methane organic gases constituted only 5% of the hydrocarbon mass and were only twice that of the diesel hydrocarbon emissions. Since diesel vehicles are customarily targeted as particulate matter and oxides of nitrogen producers, the natural gas vehicles offer an attractive alternative to the diesel units.
Emissions performance of natural gas and diesel fueled school buses with Cummins 8.3 liter engines
1999
8 Seiten, 10 Quellen
Conference paper
English
Erdgas , Dieselöl , Autobus , Abgasemission , Umweltbelastung , Umweltschutz , Lastkraftwagen , Dynamometer , Auspuffgas , Kohlenmonoxid , Methan , Gasmotor , Dieselmotor
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